Bar coding technology and computerized physician order entry (CPOE) are two technologies that have beer heralded as having the potential to substantially curb medication errors (AHRQ 2001). The use of bar coding (has received far less attention from the research community than CPOE in part because so few hospitals currently use bar coding technology for medication dispensing and administration (AHRQ 2001; ISMP, 2002), and in part from a faulty belief that such a technology will, necessarily, have positive impacts on medication error rates. We have the unique opportunity to study the impact of bar coding technology for medication dispensing and administration in a pediatric hospital with a multi-disciplinary research team composed of human factors engineers, physicians, nurses, medical informaticists and pharmacists. The implementation of the bar coding technology will be studied as a work system intervention, which means that unlike most research on technology in health care settings, the current study will examine the work system impacts of the technology, and not solely the impact on errors. A natural experiment involving a treatment and comparison pediatric hospital with 2 pre-intervention measurement points and 3 post-intervention measurements will be used to study the effects of bar coding technology on: (a) medication errors, and (b) work flow and employee working conditions and outcomes. Within the 2nd aim, technology acceptance and use will also be studied. The study of bar coding technology in a pediatric population using human factors engineering systems principles represents a significant step in health care technology and patient safety research for at least four reasons. First, medication errors account for nearly 20 percent of all medical errors, so the results of this study have implications for millions of people. Second, it is estimated that 50 percent of US hospitals are considering adopting bar coding technologies (ISMIP Medication Safety Alert, March 6, 2002). Third, by studying the system impacts of bar coding, and not just medication errors, we will be able to understand the effects of the technology on workflow, working conditions, and other system factors, all of which are critical for the successful implementation of information technology. Fourth, it is significant that this study will take place in pediatric facilities since the complexity of health care delivery is compounded with children.